Electronic fuel injection system having deceleration fuel control

ABSTRACT

Fuel is completely withheld from an internal combustion engine in response to a decrease in the demand for power from the engine when the engine speed is above the idle speed of the engine.

U V Umted States Patent 1 1 11 3,731,659

Barr et al. 1 May 8, 1973 [54] ELECTRONIC FUEL INJECTION [56] References Cited iggi agxgf DECELERATION UNITED STATES PATENTS 3,463,130 8/1969 Reichardtetal ..l23/32 EA [751 lnvemm's' 5" 1" P x l 3,515,104 6/1970 Reichardtetai ..123 32 EA 8 ia 1 3,570,460 3/1971 Rabus ..123 32 EA 5 endana 3,612,013 10/1971 Gambill ..123/32 BA [73] Assignee: General Motors Corporation, 1

Detroit, Mich. Primary Examiner-Laurence M. Goodridge Sept. 7 Assistant ExaminerCort R. Flint [21] A l N 178 27 1 Attorney-E. W. Christen et al.

[57] ABSTRACT (g1. Fuel is completely withheld from an internal [58] Fie'ld 123/32 EA bustion engine in response to a decrease in the demand for power from the engine when the engine speed is above the idle speed of the engine.

4 Claims, 6 Drawing Figures .7fi\ ng CONTROLLER H EE E ESSE'SSL -14 1? J k K I CIRCUIT F 38 j 5 L A WWW, 2 As SYNCHRONiZER TIMER A PATENTEDM'Y SHEET 3 OF 4 AT ORNEY PATENTEDKAY 81915, 3.781.659

sum u BF 4 T H+ N Na INVENTORS By [esfer MYk/kid/I Jfaarf /?Z 2790/ TIME i A TORNEY SPEED ELECTRONIC FUEL INJECTION SYSTEM HAVING DECELERATION FUEL CONTROL This invention relates to a fuel supply system for an internal combustion engine. More particularly, the invention relates to an electronic fuel injection system for completely withholding fuel from the engine in response to a decrease in the demand for power from the engine when the engine speed is above the idle speed of the engine.

Typically, in an internal combustion engine, the power output of the engine is controlled by the relative location of an adjustable throttle member between a high power position and a low power position. As the throttle member is moved toward the high power position, the demand for power from the engine increases. Conversely, as the throttle member is moved toward the low power position, the demand for power from the engine decreases. Ordinarily, the engine speed, as represented by the frequency of the engine cycles, increases in the former condition and decreases in the latter condition. For reasons of fuel consumption economy and exhaust emission control, it is often desirable to completely withhold fuel from the engine in the latter condition, provided that the engine speed is above the idle speed of the engine. The present invention provides a simple but effective technique for accomplishing this desired result.

According to a preferred embodiment of the invention, fuel is completely withheld from the engine when the amplitude of a speed signal is below the amplitude of a reference signal at the initiation of a timing pulse. The amplitude of the speed signal increases over the duration of a first fixed portion of each engine cycle so that the amplitude of the speed signal is inversely related to the speed of the engine. The timing pulse is initiated at the expiration of a second fixed portion of each engine cycle terminating within the first fixed portion. The amplitude of the reference signal is substantially constant at a first reference level as the throttle member is moved toward the high power position and is substantially constant at a second reference level as the throttle member is moved toward the lower power position. The second reference level corresponds to a lower speed limit just above the idle speed of the engine. The first reference level corresponds to an upper speed limit above the surge speed of the engine which is experienced as fuel is reapplied to the engine after having been withheld from the engine.

These and other aspects and advantages of the invention may be best understood by reference to the following detailed description of the preferred embodiment when considered in conjunction with the drawings.

In the drawings:

FIG. 1 is a block diagram of an electronic fuel injection system incorporating the principles of the invention.

FIG' 2 is a schematic diagram of a portion of the electronic fuel injection illustrated in FIG. 1.

FIG. 3 is a graphic diagram of several waveforms useful in explaining the operation of the electronic fuel injection system illustrated in FIG. 1. 7

FIG. 4 is a schematic diagram of a deceleration control circuit incorporated within the electronic fuel injection system illustrated in FIG. 1.

FIG. 5 is a graphic diagram of several waveforms useful in explaining the operation of the deceleration fuel control circuit.

FIG. 6 is a graphic diagram of a typical engine operating curve during deceleration of the engine.

Referring to FIG. 1, an internal combustion engine 10 for an automotive vehicle includes a group of eight combustion chambers or cylinders 12 which are identified C -C Preferably, the engine'10 is V-8 having a first bank of cylinders C -C C -C and a second bank of cylinders C C -C C However, it will be understood that the engine 10 may have more or less than eight cylinders 12 as desired. An output shaft or crankshaft 14 is rotatably driven in response to the occurrence of combustion within the cylinders 12 through a suitable mechanism (not shown) which normally includes a plurality of pistons and a plurality of connecting rods. A load 15, representing the drive vehicle, is connected to the crankshaft 14 through a suitable linkage. An ignition system (not shown), which conventionally includes a spark coil, a spark distributor, and spark ignitors, defines the ignition order of the cylinders 12 during each engine cycle. For the sake of convenience, it is assumed that the ignition order is C C ,,-C;,-C -C -,C ,C C per engine cycle.

A plurality of intake valves 16 each cooperate with a different associated one of the cylinders 12 for regulating the entry of combustion ingredients or air/fuel mix ture into the cylinders 12 before combustion to charge the cylinders 12. Similarly, a plurality of exhaust valves 18 each c-operate with a different associated one of the cylinders 12 for regulating the exit of combustion products or exhaust gases from the cylinders 12 after combustion to discharge the cylinders 12. An induction passage or intake manifold 20 communicates with the cylinders 12 through the intake valves 16 for transmitting air/fuel mixture through the intake valves 16 into the cylinders 12. An expulsion passage or exhaust manifold 22 communicates with each of the cylinders 12 through the exhaust valves 18 for receiving exhaust gases from the cylinders 12 through the exhaust valves 18. Conventionally, the exhaust manifold 22 is part of an exhaust system (not shown) which normally includes a muffler and an exhaust pipe. The intake valves 16 and the exhaust valves 18 are driven from the crankshaft 14 through a suitable linkage (not shown) which normally includes a camshaft, a plurality of rocker arms, and a plurality of valve lifters.

Air and fuel are combined within the intake manifold 20 to form the air/fuel mixture. Air is drawn into the intake manifold 20 through an air filter 24 which is disposed across the mouth of the intake manifold 20. A throttle valve 26 is pivotally mounted within the mouth of the intake manifold 20 just downstream from the air filter 24 for regulating the amount of air drawn into the intake manifold 20. A control element provided by the vehicle accelerator pedal 28 is connected with the throttle 26 through a suitable linkage for defining the relative location of the throttle valve 26 between a fully opened position and a fully closed position. In the fully opened position, a maximum amount of air is drawn into the intake manifold 20. Conversely, in the fully closed position, a minimum amount of air is drawn into the intake manifold 20.

An electronic fuel injection system 30 includes a group of eight fuel injectors 32 which are identified V V The fuel injectors 32 are mounted on the intake manifold 20 for individually applying fuel to corresponding ones of the eight cylinders 12 through the intake valves 16. Alternately, the fuel injectors 32 may be mounted for direct communication with the cylinders 12. Preferably, each of the fuel injectors 32 is provided by an electromagnetic valve including a plunger which is driven to a fully opened position against a spring bias when a solenoid is energized and which is driven to a fully closed position by the spring bias when the solenoid is deenergized.

A fuel supply system (not shown), which normally includes a fuel tank, a fuel pump, and a fuel pressure regulator, delivers fuel to the fuel injectors 32 at a constant pressure. A fuel control system successively energizes each of the fuel injectors 32 in accordance with a predetermined injection order during each engine cycle. Since the injection order of the fuel injectors 32 must be synchronized with the ignition order of the cylinders 12, the injection order is V,V,-V V V -V ,V,,. As the fuel injectors 32 are individually energized, fuel is deposited into the intake manifold 20 in individual atomized loads generally located adjacent to the intake valves 16 through which the atomized fuel loads are drawn into corresponding ones of the cylinders 12.

The fuel control system includes a timer 34, a controller 36, and a synchronizer 38. The timer 34 is connected between the crankshaft 14 of the engine and the synchronizer 38 for providing timing information defining the start of injection for each of the fuel injectors 32 per engine cycle. The controller 36 is connected between the throttle valve 26 of the engine 10 and the synchronizer 38 for providing control information defining theperiod of injection for each of the fuel injectors 32 per engine cycle. The synchronizer 38 is connected with each of the fuel injectors 32 for energizing the fuel injectors at time instants determined by the timer 34 and for time durations determined by the controller 36. I I

Referring to FlG.; 2, the timer 34 is provided by a magnetic pick-up transducer including a rotor 42 and a stator 44. The rotor 42 is supported at a center point for 360 rotation in a clockwise direction with respect to the stator 44. A pair of permanent magnets 46,, and 46,, are mounted on opposite ends of the rotor 42. A group of four windings 48, 48, 48,, and 48,, are mounted on the stator 44. The permanent magnets 46,, and 46,, are oppositely poled with respect to the windings 48,,48,,. That is, the permanent magnet 46,, presents a north pole to the windings 48,,48,, while the permanent magnet 46,, presents a south pole to the windings 48,,48,,.

The rotor 42 is driven from the crankshaft 14 through a suitable linkage so that the rotor 42 makes one complete revolution relative to the stator 44 per engine cycle. Hence, the angle markings to the outside of the stator 44 indicate successive 45 increments in both the position of the rotor 42 and the cycle of the engine 10. The windings 48 -48,, are located at peripheral points on the stator 44 successively spaced at angles of 45 with respect to the center point of the rotor 42. Specifically, the winding 48,, is located at the 0 point, the winding 48,, is located at the 45 point, the winding 48, is located at the 90 point and the winding 48,, is located at the 135 point. As the rotor 42 is turned relative to the stator 44, the permanent magnets 46,, and 46,, are alternately carried into and out of magnetic coupling relationship with the windings 48,,-48,, so as to produce a corresponding set of four input signals W,W., as shown in FIG. 3.

Referring to FIGS. 2 and 3, the input signals W,W., each include alternate first and second pulse pairs 50 and 52. The first pulse pairs 50 are developed in the input signals W,W as the permanent magnet 46,, successively sweeps past the windings 48,,48,,, respective ly. Alternately, the second pulse pairs 52 are developed in the input signals W,W as the permanent magnet 46,, successively sweeps past the windings 48,,48,,. The first pulse pairs 50 each exhibit a sharp negative-topositive polarity transition while the second pulse pairs 52 each exhibit a sharp positive-to-negative polarity transition. The negative-to-positive polarity transitions in the first pulse pairs 50 of the input signals W,W successively occur at the 0 point, the 45 point, the point, and the point in each engine cycle, respectively, as the centerline of the permanent magnet 46,, successively aligns with the centerlines of the windings e ggrsssaeirv 1"ss raagltmgss r e toae ative polarity transitions. in the se cond pulse barrs'sz' of the input signals W W4 successively occur at the point, the 225 point, the 270 point, and the 315 point in each engine cycle, respectively, as the centerline of the permanent magnet 46,, successively aligns with the centerlines of the windings 48,,-48,,, respectively.

For the sake of convenience, it is assumed that each 360 engine cycle is coextensive with the injection order V,V of the fuel injectors 32. That is, the beginning or 0 point of each engine cycle coincides with the start of injection for the first fuel injector V in the injection order V,V Accordingly, the negativeto-positive polarity transitions in the first pulse pairs 50 of the input signals W,W define the start of injection for the fuel injectors V,-V., in the first half of the injection order, respectively. Conversely, the positive-tonegative polarity transitions in the second pulse pairs 52 of the input signals W,W., define the start of injection for the fuel injectors V V in the second half of the injection order, respectivelyv A more detailed description of the illustrated timer or magnetic pick-up transducer 34 may be obtained by reference to U.S. patent application Ser. No. 36,055. However, it is to be noted that various alterations and modifications may be made to the timer 34 without affecting the invention. For example, the windings 48,-48 may be replaced by Hall-effect devices or any other suitable magnetic signal generating arrangement. Further, the magnetic pick-up transducer 34 may be entirely replaced by a multiple contact relay switch, a photoelectric pick-up transducer or some other equivalent contrivance.

Referring again to FIG. 2, the synchronizer 38 includes a group of four bistable multivibrators or flipflops 54,,54,,. The group of input windings 48,,-48,, of the magnetic pick-up transducer 34, are connected to corresponding ones of the group of flip-flops 54,,54,, of the synchronizer 38, respectively. The flip-flops 54,-54 are responsive to the input signals W,W to provide a corresponding set of four symmetrical timing signals A,-A respectively, as shown in FIG. 3. The timing signals A,-A, are square waves each exhibiting periodic magnitude permutations or amplitude transitions between a relatively high level and a relatively low level. Thus, the timing signals A,A shift to the high level in response to the occurrence of the negative-topositive polarity transitions in the first pulse pairs 50 of the input signals W,-W.,, respectively. Alternately, the timing signals A,A shift to the low level in response to the occurrence of the positive-to-negative polarity transitions in the second pulse pairs 52 of the input signals W W respectively. As a result, the timing signals A A., each contain two magnitude permutations or amplitude transitions per engine cycle.

More particularly, in the timing signal A a low-tohigh level transition occurs at the point and a highto-low level transition occurs at the 180 point in each engine cycle marking the start of injection for the fuel injectors V and V respectively. In the timing signal A a low-to-high level transition occurs at the 45 point and a high-to-low level transition occurs at the 225 point in each engine cycle marking the start of injection for the fuel injectors V and V respectively. In the timing signal A a low-to-high level transition occurs at the 90 point and a high-to-low level transition occurs at the 270 point marking the start of injection for the fuel injectors V and V respectively. In the timing signal A.,, a low-to-high level transition occurs at the 135 point and a high-to-low level transition occurs at the 3 l5 point in each engine cycle marking the start of injection for the fuel injectors V and V respectively. Accordingly, the magnitude permutations or level transitions in the set of timing signals A,A., are successively spaced at intervals of 180 or one-half of an engine cycle within each of the timing signals A,A and are successively displaced at intervals of 45 or oneeighth an engine cycle between each of the timing signals A,A

The synchronizer 38 multiplexes the set of timing signals A,-A to obtain a single timing signal E as shown in FIG. 3. Like the timing signals A,A the timing signal E exhibits periodic magnitude permutations or amplitude transitions between a relatively high level and a relatively low level. Specifically, the timing signal E shifts to the relatively low level in response to each of the level transitions in the timing signals A, and A and shifts to the relatively high level in response to each of the level transitions in the timing signals A and A Accordingly, the magnitude permutations or amplitude transitions in the single timing signal E are successively spaced at intervals of 45 or one-eighth of an engine cycle. Hence, during each engine cycle, the timing signal E contains eight level transitions successively defining the start of injection for each of the eight fuel injectors r' su' Referring to FIG. 1, the single timing signal E is applied from the synchronizer 38 to the controller 36 via a timing line 56. The controller 36 is responsive to the single timing signal E to provide a single pulse train F as shown in FIG. 3. The single pulse train F contains eight bilevel control pulses per engine cycle synchronized with the eight level transitions per engine cycle in the timing signal E. That is, the control pulses in the single pulse train F are each initiated in response to the occurrence of a corresponding one of the level transitions in the single timing signal E. As previously described, the occurrence of each of the eight level transitions in the timing signal E defines the start of injection for a corresponding one of the eight fuel injectors 32 according to the injection order V,V during each engine cycle. Likewise, the duration of each of the eight control pulses defines the period injection for a corresponding one of the fuel injectors 32 according to the injection order V,V during each engine cycle.

More specifically, the controller 36 determines the duration of each of the control pulses in the single pulse train F as a function of at least one operating parameter of the engine 10. As illustrated, the controller 36 is responsive to the relative position of the throttle valve 26. Alternately, the controller 36 may be responsive to the negative pressure or vacuum within the intake manifold 20. Moreover, the duration of the control pulses in the single pulse train F may be defined by the controller 36 in response to additional engine operating parameters such as engine temperature and battery voltage. In any event, since the controller 36 is only incidental to the present invention, it is not described in detail. A more detailed description of one embodiment of the controller 36 may be obtained from US. patent application Ser. No. 36,055.

In order to achieve satisfactory performance in most V-8 engines such as the engine 10, it is necessary that the period of injection for the fuel injectors V,V approach a maximum duration of or one half of an engine cycle at relatively high speeds and relatively high loads. In other words, the individual. injection periods for the fuel injectors V,V must overlap one another. However, the control pulses in the single pulse train F cannot overlap one another. The maximum time available between successive level transitions in the single timing signal F is 45 or one-eighth of an engine cycle. Consequently, the controller 36 determines the duration of the control pulses in the single pulse train F as a fraction or a percentage of the maximum time available between successive level transitions in the single timing signal F. As a result, the duration of the control pulses in the single pulse signal F is less than the desired period of injection for the fuel injectors v, v, by a factor of four.

Referring to FIG. 1, the single control pulse train F is applied from the controller 36 to the synchronizer 38 over a control line 58. The synchronizer 38 separates the individual control pulses from the single pulse train F and expands the duration of the separated control pulses by a factor of four to conform the actual duration-of the control pulses with the desired period of injection for the fuel injectors V,V As a result, the synchronizer 38 provides a series of eight pulse trains 1 -1 as shown in FIG. 3. The control pulses in the series of pulse trains 1,-1, are successively initiated at intervals of 360 or one engine cycle within each of the pulse trains l,l,, and are successively displaced at intervals of 45 or one-eighth of an engine cycle between each of the pulse trains I 1 Hence, the eight pulse trains l,-l each contain control pulses for a corresponding one of the eight fuel injectors V, -V,,.

The synchronizer 38 applies the pulse trains l,-l to energize corresponding ones of the fuel injectors V,V for e ta n Qftb 9 mm n sss at e P ls t i l -l Thus, the fuel injectors V -V are opened for the duration of the control pulses in the pulse trains Ir'lg to inject fuel aLa constant rate to the C1 Cg of the engine 10 through the intake man 361320 and the intake valves 16.

For a more detailed description of one embodiment of the synchronizer 38, reference may be made to copending U.S. patent application Al5,367. However, at this point, it is to be understood that the generalized electronic fuel injection system so far illus trated is shown only to facilitate a more complete understanding of the invention. As will become more apparent later, the invention may be effectively applied to virtually any type of an electronic fuel injection system.

Referring to FIG. 1, the power output of the engine 10 is defined by the relative position of the throttle valve 26 as controlled by the vehicle accelerator pedal 28. As the throttle valve 26 is moved toward the fully opened position or the high power position, more air is drawn into the intake manifold 20 to increase the demand for power from the engine 10. As a result, the controller 36 increases the duration of the control pulses applied to the fuel injectors 32 thereby increasing the amount of fuel injected into the intake manifold 20. Assuming the load 15 on the engine 10 remains relatively constant, the engine speed increases as the engine l accelerates in response to the increased quantity of air/fuel mixture applied from the intake manifold 20. Conversely as the throttle valve 26 is moved toward the fully closed position or the low power position, a minimum amount of air is drawn into the intake manifold 20 thereby decreasing the demand for power from the engine 10. Accordingly, the controller 36 decreases the duration of the control pulses applied to the fuel injectors 30 thereby decreasing the amount of fuel injected into the intake manifold 20. Again, assuming the load 15 on the engine remains relatively constant, the engine speed decreases as the engine 10 decelerates in response to the decreased quantity of air/fuel mixture applied from the intake manifold 20.

During deceleration of the engine 10, any fuel consumed within the cylinders 12 is largely wasted since the load 15 is actually driving the engine 10 rather than vice versa. In addition, during deceleration of the engine 10, the exhaust gases expelled from the cylinders 12 contain a higher proportion of deleterious exhaust emissions than at other times. Hence, it is desirable to disable the electronic fuel injection system 30 to completely stop the injection of fuel into the intake manifold during deceleration of the engine 10. However, as the speed of the engine 10 approaches the desired idle speed, it is necessary to again apply fuel to the engine 10 to maintain the idle speed and prevent the engine 10 from stalling. Accordingly, the present invention provides a deceleration fuel control circuit 60 for completely withholding fuel from the engine 10 in response to a decrease in the demand for power from the engine 10 when the engine speed is above the idle speed of the engine 10.

Referring to FIG. 1, the deceleration fuel control circuit 60 includes a pair of electrical inputs connected to the synchronizer 38 over a pair of input lines 62 and 64 and a mechanical input connected to the throttle valve 26 through a suitable linkage 66. More specifically, as shown in FIG. 2, the input line 62 is connected to the output of the flip-flip 54,, in the synchronizer 38 while the input line 64 is connected to the output of the flipflop 54,. in the synchronizer 38. Further, the deceleration fuel control circuit 60 includes an electrical output connected to the control line 58 over an output line 68.

In operation, the deceleration fuel control circuit 60 is responsive to the timing signals A and A on the input lines 62 and 64 to determine the speed of the engine 10. Further, the deceleration fuel control circuit 60 is responsive through the linkage 66 to movement of the throttle valve 26 toward the low power position when the engine speed is above the idle speed of the engine 10 to ground the control line 58 through the output line 68. As a result, the electronic fuel injection system 30 is disabled to completely withhold fuel from the engine 10.

Referring to FIG. 4, an electrical power supply 70 is provided for the deceleration fuel control circuit 60. The power supply 70 includes a source of direct current voltage 72 which may be provided by the vehicle battery. The voltage source 72 applies a supply voltage between a high potential line 74 and a low potential line 76 through a control switch 78 which may be provided by the vehicle ignition switch. Of course, it will be readily appreciated that the supply voltage provided by the power supply 70 may also be applied to energize the controller 36 and the synchronizer 38 of the electronic fuel injection system 30.

Referring to FIGS. 4 and 5, the deceleration fuel control circuit 60 includes a speed signal generator 80 for providing a speed signal S at a junction 82. The speed signal generator 80 includes a capacitor 84, a re sistor 86, and a PNP junction transistor 88. The capacitor 84 is connected between the junction 82 and the low potential line 76. The resistor 86 is connected between the junction 82 and the high potential line 74. The emitter electrode of the transistor 88 is connected directly to the junction 82 while the collector electrode of the transistor 88 is connected directly to the low potential line 76. The base electrode of the transistor 88 is connected directly to the output of the flip-flop 54,, in the synchronizer 38 via the input line 62.

The timing signal A,, as shown in FIG. 5, is applied to the base electrode of the transistor 88 via the input line 62. Hence, the synchronizer 38 acts as a timing signal generator. The timing signal A alternately shifts between a relatively high level and a relatively low level. Specifically, the timing signal A is at the high level for the duration of a first fixed portion of each engine cycle as represented by the time period T which is approximately equal to or one-half of an engine cycle.

As the timing signal A, shifts from the relatively high level to the relatively low level, the transistor 88 is rendered fully conductive. With the transistor 88 turned on, the capacitor 84 discharges through the transistor 88. In this condition, the amplitude of the speed signal S at the junction 82 is effectively clamped at a base level L defined by the ground potential on the low potential line 76. As the timing signal A shifts from the relatively low level to the relatively high level, the transistor 88 is rendered fully nonconductive. With the transistor 88 turned off, the capacitor 84 charges through the resistor 86. In this condition, the amplitude of the speed signal S at the junction 82 increases from the base level L,, toward a maximum level L, defined by the supply potential on the high potential line 74.

Thus, the amplitude of the speed signal S unidirectionally increases from the base level L,, toward the maximum level L, over the duration of the time period T More particularly, the amplitude of the speed signal S increases in accordance with an RC time constant provided by the resistor 86 and the capacitor 84. Preferably, this RC time constant is selected such that the increase in the amplitude of the speed signal S is substantially linear over the time period T Alternately, the resistor 86 may be replaced by a constant current source.

A reference signal generator 90 includes a voltage divider network 92 and an NPN junction transistor 94. The voltage divider network 92 includes biasing resistors 96, 98, and 100. The resistor 96 is connected between ajunction 102 and the high potential line 74. The resistor 98 is connected between the junction 102 and a junction 104. The resistor 100 is connected between the junction 104 and the low potential line 76. The emitter electrode of the transistor 94 is connected directly to the low potential line 76. The collector electrode of the transistor 94 is connected directly to the junction 104.

The reference signal generator 90 develops a reference signal R at the junction 102. The amplitude of the reference signal R is substantially constant at either an upper reference level L or a lower reference level L depending upon the conductive condition of the transistor 94. When the transistor 94 is fully conductive, the reference signal R is at the lower reference level L,, as defined by the voltage divider action of the resistors 96 and 98. When the transistor 94 is rendered fully nonconductive, the amplitude of the reference signal R is substantially constant at the upper reference level L as defined by the voltage divider action of the resistors 96, 98, and 100. The significance of the upper reference level L and the lower reference level L, will be more fully described later. At this point, it is sufficient to note that the transistor 94 is normally turned on so that the amplitude of the reference voltage R is normally at the lower reference level L,,.

A differential switch or differential amplifier 106 includes NPN junction transistors 108, 110, and 112. The collector electrode of the transistor 108 is connected directly to a junction 114 between the emitter electrodes of the transistors 110 and 112. The emitter electrode of the transistor 108 is connected through a biasing resistor 116 to the low potential line 76. The base electrode of the transistor 108 is connected directly to a junction 118. A biasing resistor 120 is connected between the junction 118 and the high potential line 74. A temperature compensating diode 122 and a biasing resistor 124 are connected in series between the junction 118 and the low potential line 76. The base electrode of the transistor 110 is connected directly to the junction 82 in the speed signal generator 80. The base electrode of the transistor 112 is connected directly to the junction 102 in the reference signal generator 90. The collector electrode of the transistor 110 is connected through a biasing resistor 126 to the high potential line 74. Similarly, the collector electrode of the transistor 112 is connected through a biasing resistor 128 to the high potential line 74.

in the differential amplifier 106, the transistor 108 is rendered conductive in a constant current mode through the biasing action of the resistors 116, 120, and 124. Hence, the transistor 108 provides a constant current sink for the transistors 110 and 1 12 at the junction 114. In the conventional manner, the differential amplifier 106 is operable between first and second states. In the first state, the transistor 112 is rendered fully conductive while the transistor is rendered fully nonconductive. Conversely, in the second state, the transistor 110 is rendered fully conductive and the transistor 112 is rendered fully nonconductive. The differential amplifier 106 switches from the first state to the second state when the amplitude of the speed signal S at the junction 82 exceeds the amplitude of the reference signal R at the junction 102. Alternately, the differential amplifier 106 switches from the second state to the first state when the amplitude of the reference signal R at the junction 102 exceeds the amplitude of the speed signal S at the junction 82.

A timing pulse generator 130 includes a differentiator 132, a pulse amplifier 134, and first and second logic gates 136 and 138. The differentiator 132 includes a coupling capacitor 140, a pair of biasing re sistors 142 and 144, and a diode 146. The capacitor 140 is connected between a junction 148 and the output of the bistable flip-flop 54 in the synchronizer 38 via the input line 64. The biasing resistor 142 is connected between the junction 148 and the high potential line 74. The biasing resistor 144 is connected between the junction 148 and the low potential line 76.

The pulse amplifier 134 includes NPN junction transistors and 152. The base electrode of the transistor 150 is connected through the diode 146 to the junction 148 in the differentiator 132. The collector electrode of the transistor 150 is connected directly to the high potential line 74. The emitter electrode of the transistor 150 is connected through a biasing resistor 154 to the base electrode of the transistor 152. The emitter electrode of the transistor 152 is connected directly to the low potential line 76. The collector electrode of the transistor 152 is connected through a biasing resistor 156 to the high potential line 74.

The first logic gate 136 includes an NPN junction transistor 158 and a PNP junction transistor 160. Similarly, the second logic gate 138 includes an NPN junction transistor 162 and a PNP junction transistor 164. The base electrode of the transistor 158 is connected through a biasing resistor 166 to the collector electrode of the transistor 152. The base electrode of the transistor 162 is connected through a biasing resistor 168 to the collector electrode of the transistor 152. The emitter electrodes of the transistors 158 and 162 are connected together directly to the low potential line 76. The collector electrode of the transistor 158 is connected directly to a junction 170 while the collector electrode of the transistor 162 is connected directly to a junction 172. The base electrode of the transistor is connected directly to the collector electrode of the transistor 1 10 in the differential amplifier 106. The base electrode of the transistor 164 is connected directly to the collector electrode of the transistor 112 in the differential amplifier 106. The emitter electrodes of the transistors 160 and 164 are connected together directly to the high potential line 74. The collector electrode of the transistor 160 is connected through a biasing resistor 174 to the junction while the collector electrode of the transistor 164 is connected through a biasing resistor 176 to the junction 172.

The timing signal A as shown in FIG. 5, is applied to the differentiator 132 over the input line 64. Like the timing signal A the timing signal A; alternately shifts between a relatively high level and a relatively low level. However, the timing signal A is displaced 90 or one-quarter of an engine cycle with respect to the timing signal A As a result, the timing signal A shifts from the low level to the high level at the midpoint of the time period T during which the timing signal A is at the high level. In other words, the timing signal A exhibits a low-to-high level transition at the expiration of a second fixed portion of each engine cycle as represented by the time period T which is equal to 90 or one-quarter of an engine cycle. Thus, the time period T is contained within and terminates within the time period T Regardless of the frequency of the timing signals A and A the relationship between the time periods T and T remains the same. Thus, as the speed of the engine increases, the time periods T and T both proportionally decrease.

In the differentiator 132, the capacitor 140 combines with the resistors 142 and 144 to differentiate the timing signal A As a result, timing pulses P of positive polarity are developed at the junction 148 when the timing signal A shifts from the low level to the high level. In particular, a timing pulse P is initiated as the timing signal A undergoes a low-to-high level transition. When a timing pulse P is absent from the junction 148, the transistor 150 is rendered relatively nonconductive through the biasing action of the diode 146 and the resistors 142 and 144. With the transistor 150 relatively nonconductive, the transistor 152 is rendered fully nonconductive through the biasing action of the resistor 154 and the transistor 150. However, when a timing pulse P is present at the junction 148, the transistor 150 is momentarily rendered highly conductive. With the transistor 150 momentarily highly conductive, the transistor 152 is momentarily fully conductive. With the transistor 152 momentarily turned on, the timing pulse P at the junction 148 is amplified and inverted to provide an inverse timing pulse P at the collector electrode of the transistor 152.

When the differential amplifier 106 is in the first state, the transistor 112 is rendered fully conductive and the transistor 110 is rendered fully nonconductive. With the transistor 112 turned on, the transistor 164 in the logic gate 138 is rendered fully conductive through the biasing action of the transistors 108 and 112 and the resistors 116 and 128. With the transistor 110 turned off, the transistor 160 in the logic gate 136 is rendered fully nonconductive through the biasing action of the resistor 126. Conversely, when the differential amplifier 106 is in the second state, the transistor 110 is rendered fully conductive and the transistor 110 turned on, the transistor 160 in the logic gate 136 is rendered fully conductive through the biasing action of the transistors 108 and 110 and the resistors 116 and 126. With the transistor 112 turned off, the transistor 164 in the logic gate 138 is rendered fully nonconductive through the biasing action of the resistor 128.

When the transistor 152 is turned off so that an inverse timing pulse 1 is not present at the collector electrode of the transistor 152, the transistor 158 in the logic gate 136 is conditioned to turn on through the biasing action of the resistors 156 and 166 while the transistor 162 in the logic gate 138 is conditioned to turn on through the biasing action of the resistors 156 and 168. If the differential amplifier 106 is in the second state so that the transistor is turned on, the transistor 158 is rendered fully conductive in response to the absence of an inverse timing pulse P. With the transistor 158 turned on the junction is effectively clamped to the ground potential on the low potential line 76 through the transistor 158. On the other hand, if the differential amplifier 1116 is in the first state so that the transistor 164 is turned on, the transistor 162 in the logic gate 138 is rendered fully conductive in response to the absence of an inverse timing pulse P. With the transistor 162 turned on, the junction 172 is effectively clamped to the ground potential on the low potential line 76 through the transistor 162. Hence, regardless of the state of the differential amplifier 106, no timing pulses are developed at the junctions 170 and 172 when the transistor 152 is turned 011'.

When the transistor 152 is turned on so that an in verse timing pulse P is present at the collector electrode of the transistor 152, the transistors 158 and 162 are both momentarily turned off. The transistor 158 in the logic gate 136 is rendered fully nonconductive through the biasing action of the resistors 156 and 166 while the transistor 162 in the logic gate 138 is rendered fully nonconductive through the biasing action of the resistors 156 and 168. With the transistor 158 momentarily turned off, the junction 170 is momentarily unclamped from the low potential line 76 to develop a timing pulse P of positive polarity at the junction 170, provided that the differential amplifier 106 is in the second state so that the transistor 160 is turned on. Similarly, with the transistor 162 momentarily turned off, the junction 172 is unclamped to develop a timing pulse P of positive polarity at the junction 172, provided that the differential amplifier 106 is in the first state so that the transistor 164 is turned on. Accordingly, when the differential amplifier 106 is in the first state, any timing pulses developed by the differentiator 132 are amplified by the pulse amplifier 134 and applied to the junction 172 by the second logic gate 138. Altemately, when the differential amplifier 106 is in the second state, any timing pulses developed by the differentiator 132 are amplified by the pulse amplifier 134 and applied to the junction 170 by the second logic gate 136.

A pulse switch or bistable multivibrator 178 includes a pair of NPN junction transistors 180 and 182. The emitter electrodes of the transistors 1811 and 182 are connected together to the low potential line 76. The collector electrode of the transistor 180 is connected through a biasing resistor 184 to the high potential line 74 and is connected through a biasing resistor 186 to the base electrode of the transistor 182. The collector electrode of the transistor 182 is connected through a biasing resistor 188 to the high potential line 74 and is connected through a biasing resistor 190 to the base electrode of the transistor 180. The base electrode of the transistor 180 is connected through a biasing resistor 192 to the low potential line 76 and is connected through a coupling diode 194 to the junction 1711 in the timing pulse generator 130. The base electrode of the transistor 182 is connected through a biasing resistor 196 to the ground line 76 and is connected through a coupling diode 198 to the junction 172 in the timing pulse generator 130.

When a timing pulse P appears at the junction 172, it is coupled through the diode 198 and the resistor 196 to the base electrode of the transistor 182. As a result, the transistor 182 is rendered fully conductive. With the transistor 182 turned on, the transistor 180 is rendered fully nonconductive through the biasing action of the transistor 182 and the resistor 190. With the transistor 180 turned off, the transistor 182 is maintained turned on through the biasing action of the resistors 184, 186, and 196. This is the first state of the bistable multivibrator 178. Alternately, when a timing pulse P appears at the junction 170, it is coupled through the diode 194 and the resistor 192 to the base electrode of the transistor 180. Consequently, the transistor 180 is rendered fully conductive. With the transistor 180 turned on, the transistor 182 is rendered fully nonconductive through the biasing action of the transistor 180 and the resistor 186. With the transistor 182 turned off, the transistor 180 is maintained turned on through the biasing action of the resistors 188, 190, and 192. This is the second state of the bistable multivibrator 178.

It will now be apparent that whether the bistable multivibrator 178 resides in the first state or in the second state is dependent upon the relative relationship between the amplitude of the speed signal S and the amplitude of the reference signal R at the initiation of each timing pulse P. Thus, each timing pulse P which is initiated when the amplitude of the speed signal S exceeds the amplitude of the reference signal R, is applied to trigger the bistable multivibrator 178 to the second state. Alternately, each timing pulse P which is initiated when the amplitude of the reference signal R exceeds the amplitude of the speed signal S is applied to trigger the bistable multivibrator 178 to the first state. Of course, once the bistable multivibrator 178 is triggered to one of the first and second states, it remains in that state until it is triggered to the other of the first and second states.

A buffer switch 200 includes a pair of NPN junction transistors 202 and 204. The base electrode of the transistor 202 is connected directly to the collector electrode of the transistor 182 in the bistable multivibrator 178. The collector electrode of the transistor 202 is connected directly to the high potential line 74.

The emitter electrode of the transistor 202 is connected through a biasing resistor 206 to the base electrode of the transistor 204 and through a biasing resistor 207 to the base electrode of the transistor 94 in the reference signal generator 90. The emitter electrode of the transistor 204 is connected directly to the low potential line 76. The collector electrode of the transistor 204 is connected through a biasing resistor 208 to the high potential line 74.

When the bistable multivibrator 178 is in the first state, the transistor 182 is rendered fully conductive. With the transistor 182 turned on, the transistor 202 is rendered relatively nonconductive. With the transistor 202 relatively nonconductive, the transistor 204 is rendered fully nonconductive through the biasing action of the resistor 206 and the transistor 202. Similarly, the transistor 94 is rendered fully nonconductive through the biasing action of the resistor 207 and the transistor 202. With the transistor 94 turned off, the reference signal R is at the upper reference level L When the bistable multivibrator 178 is in the second state, the transistor 182 is rendered fully nonconductive. With the transistor 182 turned off, the transistor 202 is rendered highly conductive, the transistor 204 is rendered fully conductive through the biasing action of the resistor 206 and the transistor 202. Likewise, the transistor 94 is rendered fully conductive through the biasing action of the resistor 207 and the transistor 202. With the transistor 94 turned on, the reference signal R is at the lower reference level L A control switch or throttle switch 210 is schematically illustrated as including a pair of switch terminals 212 and 214 and a switch arm 216. The arm 216 is pivotably movable about the terminal 212 into and out of electrical contact with the terminal 214. When the throttle switch 210 is in a closed position, the arm 216 is in electrical contact with the terminal 214. When the throttle switch 210 is in an opened position, the arm 216 is out of electrical contact with the terminal 214. A conventional dashpot device 218 is connected to the switch arm 216 through a push rod 220 and is connected to the throttle valve 26 through the linkage 66. The dashpot device 218 is responsive to movement of the throttle valve 26 toward the closed position at a predetermined rate to place the throttle switch 210 in the closed position.

The terminal 212 of the throttle switch 210 is connected directly to the collector electrode of the transistor 204 in the buffer switch 200. The terminal 214 of the throttle switch 210 is connected directly to the base electrode of an output transistor 224. The emitter electrode of the transistor 224 is connected directly to the low potential line 76. The collector electrode of the transistor 224 is connected directly to the control line 58 between the controller 36 and the synchronizer 38 through the output line 68.

When the throttle switch 210 is in the opened position in response to acceleration or steady running of the engine 10, the transistor 224 is rendered fully nonconductive. With the transistor 224 turned off, the control line 58 is uneffected by the deceleration fuel control circuit 60. Accordingly, the electronic fuel injection system 30 is placed in an enabled condition. How ever, when the throttle switch 210 is in the closed posi tion in response to deceleration of the engine 10, the conductive condition of the transistor 224 is dependent upon the conductive condition of the transistor 204 in the buffer switch 200. If the transistor 204 is turned on, the transistor 224 remains fully nonconductive through the biasing action of the transistor 204. Conversely, if the transistor 204 is turned off, the transistor 224 is rendered fully conductive through the throttle switch 210 and the biasing action of the resistor 208. With the transistor 224 turned on, the control line 58 is effectively clamped to the ground potential on the low potential line 74 through the output line 68 and the transistor 224. Consequently, the electronic fuel injection system 30 is placed in a disabled condition in which no control pulses are applied from the controller 36 to the synchronizer 38. Thus, the fuel injectors 32 are deenergized to completely withhold fuel from the engine 10.

The general operation of the deceleration fuel control circuit 60 may be best understood by reference to FIGS. 4, 5, and 6. FIG. 6 depicts a typical deceleration operating curve for the engine 10 in terms of speed and time. Before time 1 the accelerator pedal 28 of the engine 10 is actuated to pivot the throttle valve 26 toward the fully opened position or the high power position thereby to increase the demand for power from the engine 10. With the throttle valve 26 moved toward the fully opened position, the throttle switch 210 is placed in the opened position. With the throttle switch 210 in the opened position, the transistor 224 is turned off to enable the electronic fuel injection system 30. In the enabled condition, the electronic fuel injection system 30 applies fuel to the engine 10. Further, with the throttle valve 26 moved toward the fully opened position, the speed of the engine 10 increases.

Initially, the engine speed increases from below an upper speed level N before the time I With the speed of the engine 10 below the upper speed level N the amplitude of the speed signal S always exceeds the amplitude of the reference signal R at the initiation of each of the timing pulses P as shown by the in FIG. 5b. Hence, the timing pulses P are applied to trigger the bistable multivibrator 178 to the second state. With the bistable multivibrator 178 in the second state, the transistor 94 is turned on to define the amplitude of the reference signal R at the lower reference level L,,. The lower reference level L is set such that the amplitude of the speed signal S at the initiation of each of the timing pulses P just falls below the lower reference level L, as the speed of the engine 10 increases through the upper speed level N As the engine 10 accelerates before time 1,, the engine speed increases through the upper speed level N With the speed of the engine 10 above the upper speed level N the amplitude of the reference signal R at the lower reference level l always exceeds the amplitude of the speed signal S at the initiation of each of the timing pulses P as shown by the in FIG. c. Thus, the timing pulses P are applied to trigger the bistable multivibrator 178 to the first state. With the bistable multivibrator 178 in the first state, the transistor 94 is turned off to define the amplitude of the reference signal R at the upper reference level L,,. The upper reference level L is set such that the amplitude of the speed signal S at the initiation of each of the timing pulses P just rises above the upper reference level L as the speed of the engine decreases through a lower speed limit N,,.

At time 1,, the accelerator pedal 28 of the engine 10 is actuated to pivot the throttle valve 26 toward the fully closed position or the low power position to decrease the demand for power from the engine 10. With the throttle valve 26 moved toward the fully closed position, the throttle switch 210 is placed in the closed position. With the throttle switch 210 in the closed position and the bistable multivibrator in the second state, the transistor 224 is turned on to disable the electronic fuel injection system 30. In the disabled condition, the electronic fuel injection system 30 completely withholds fuel from the engine 10. Moreover, with the throttle valve 26 moved toward the fully closed position, the speed of the engine 10 decreases.

As the engine decelerates after time t,, the engine speed decreases through the upper speed level N toward the lower speed level N At time t the engine speed decreases through the lower speed level N With the speed of the engine 10 below the lower speed level N the amplitude of the speed signal S at the initiation of each of the timing pulses P always exceeds the amplitude of the reference signal R at the upper reference level L as shown by the in FIG. 5a. Hence, the timing pulses P are applied to trigger the bistable multivibrator 178 to the second state. With the bistable multivibrator 178 in the second state, the transistor 224 is turned off to enable the electronic fuel injection system 30 even though the throttle switch 210 remains in the closed position. In the enabled condition, the

electronic fuel injection system 30 again applies fuel to the engine 10.

In addition, with the bistable multivibrator 178 in the second state after time t the transistor 94 is turned on to define the amplitude of the reference signal R at the lower reference level L,,. Further, as fuel is applied to the engine 10 after time t the engine experiences a transient surge condition. That is, the speed of the engine l0 initially rapidly increases above the lower speed level N and subsequently gradually decreases below the lower speed level N However, the peak speed of the engine 10 during this transient surge condition is well below the upper speed level N Thus, with the amplitude of the reference signal R at the lower reference level L the amplitude of the speed signal S always exceeds the amplitude of the reference signal R at the initiation of each of the timing pulses 1P during the transient surge condition. Therefore, the transistor 224 remains turned off to continuously enable the electronic fuel injection system 30.'At time t;,, the speed of the engine 110 finally stabilizes at an idle speed level N, which is slightly below the lower speed level N Hence, a hysteresis is provided between the upper and lower speed levels N, and N to prevent the speed of the engine 10 from hunting or oscillating about the lower speed level N It will now be appreciated that the present invention provides a simple but effective technique for completely withholding fuel from an internal combustion engine in response to a decrease in the demand for power from the engine when the engine speed is above the idle speed of the engine. However, it is to be understood thatthe preferred embodiment of the invention is shown for illustrative purposes only and that various modifications and alterations may be made to the preferred embodiment without departing from the spirit and scope of the invention.

What is claimed is:

1. In an internal combustion engine exhibiting periodic engine cycles having a frequency proportional to the speed of the engine and including a throttle member operable to decrease the demand for power from the engine, the combination comprising: fuel injection means for applying fuel to the engine when enabled and for withholding fuel from the engine when disablecl; means for developing a speed signal having an amplitude which increases over the duration of a first fixed portion of each engine cycle such that the amplitude of the speed signal is inversely related to the speed of the engine; means for developing a timing signal having magnitude permutations each occurring at the expiration of a second fixed portion of each engine cycle which terminates within the first fixed portion; and means for disabling the fuel injection means to withhold fuel from the engine in response to a decrease in the demand for power from the engine when the amplitude of the speed signal at the occurrence of a magnitude permutation in the timing signal is below a reference level corresponding to an engine speed above the idle speed of the engine.

2. In an internal combustion engine exhibiting periodic engine cycles having a frequency proportional to the speed of the engine and including a throttle member operable to decrease the demand for power from the engine, the combination comprising: fuel injection means for applying fuel to the engine when in an enabled condition and for withholding fuel from the engine when in a disabled condition; means for developing a speed signal having an amplitude which increases over the duration of a first fixed portion of each engine cycle such that the amplitude of the speed signal is inversely related to the speed of the engine; means for developing timing pulses each initiated at the expiration of a second fixed portion of each engine cycle which terminates within the first fixed portion; means including a throttle switch operable from a deactuated position to an actuated position in response to a decrease in the demand for power from the engine; and means for placing the fuel injection means in the disabled condition to withhold fuel from the engine when the throttle switch is in the actuated position and the amplitude of the speed signal at the initiation of a timing pulse is below reference level corresponding to an engine speed above the idle speed of the engine.

3. In an internal combustion engine exhibiting periodic engine cycles having a frequency proportional to the speed of the engine and including a throttle member operable to decrease the demand for power from the engine, the combination comprising: fuel injection means for applying fuel to the engine when in an enabled condition and for withholding fuel from the engine when in a disabled condition; speed signal generator means for developing a speed signal having an amplitude which increases over the duration of a first fixed portion of each engine cycle such that the amplitude of the speed signal is inversely related to the speed of the engine; reference signal generator means for developing a reference signal having an amplitude which is substantially constant at a reference level corresponding to an engine speed above the idle speed of the engine; differential switching means operable to a first state when the amplitude of the reference signal exceeds the amplitude of the speed signal and operable to a second state when the amplitude of the speed signal exceeds the amplitude of the reference signal; timing pulse generator means for developing timing pulses each initiated at the expiration of a second fixed portion of each engine cycle which terminates within the first fixed portion; means including a throttle switch operable from a first position to a second position in response to a decrease in the demand for power from the engine; and means for placing the fuel injection means in the disabled condition to withhold fuel from the engine when the throttle switch is in the second position and the differential switching means is in the first state at the initiation of a timing pulse.

In an internal combustion engine exhibiting periodic engine cycles having a frequency proportional to the speed of the engine and including a throttle member movable to decrease the demand for power from the engine, the combination comprising: fuel injection means for applying fuel to the engine when in an enabled condition and for withholding fuel from the engine when in a disabled condition; speed signal generator means for developing a speed signal having an amplitude which increases from a base level toward a maximum level over the duration of a first fixed portion of each engine cycle such that the amplitude of the speed signal is inversely related to the speed of the engine; reference signal generator means for developing a reference signal having an amplitude which is substantially constant; differential switching means operable to a first state when the amplitude of the reference signal exceeds the amplitude of the speed signal and operable to a second state when the amplitude of the speed signal exceeds the amplitude of the reference signal; timing pulse generator means for developing timing pulses each initiated at the expiration of a second fixed portion of each engine cycle which terminates within the first fixed portion; means including a throttle switch operable from a first position to a second position in response to movement of the throttle member to decrease the demand for power from he engine; bistable switching means operable to a first state from a second state when the throttle switch is in the second position and the differential switching means is in the first state at the initiation of a timing pulse; means for placing the fuel injection means in the disabled condition to withhold fuel from the engine when the bistable switching means is in the first state; and the reference voltage generator means including means for defining the amplitude of the reference signal at a lower reference level located between the base level and the maximum level at a point corresponding to an engine speed slightly above the idle speed of the engine when the bistable switching means is in the first state and for defining the amplitude of the reference signal at an upper reference level located between the base level and the maximum level at a point corresponding to an engine speed above the peak speed of the engine experienced when fuel is reapplied to the engine after having been withheld from the engine when the bistable switching means is in the second state.

7 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3'73l:659 Dated May 8, 1973 Inventor (s Paul N. Barr et al It: is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

r- Column 2, line 15 "drive should read driven line 22, "C should read C2 line 28, "c-operate" should read cooperate line 65, "v should read V Column 3, line 18, "V -V should read -V -V Column 4-, line 22, "48 -48 should read 48 -48 --7 line 50, "48 -48" should read 48 -485 line 63, "54 -54" should read 54 54 Column 5 line 53, "V -V should read V1-V Column 6, line 42, a ter "four" insert (4) line 48, after "four" insert (4) line 63, "I -I should read 1 -1 Column 18, line 36, "he" should read the-.-.

Signed and sealed this 9th day of April ,19714.

(SEAL) Attest:

EDWARD MJ LEJTCI-IER,JR 'C. MARSHALL DANN Attesting; Officer I Commissioner of Patents 

1. In an internal combustion engine exhibiting periodic engine cycles having a frequency proportional to the speed of the engine and including a throttle member operable to decrease the demand for power from the engine, the combination comprising: fuel injection means for applying fuel to the engine when enabled and for withholding fuel from the engine when disabled; means for developing a speed signal having an amplitude which increases over the duration of a first fixed portion of each engine cycle such that the amplitude of the speed signal is inversely related to the speed of the engine; means for developing a timing signal having magnitude permutations each occurring at the expiration of a second fixed portion of each engine cycle which terminates within the first fixed portion; and means for disabling the fuel injection means to withhold fuel from the engine in response to a decrease in the demand for power from the engine when the amplitude of the speed signal at the occurrence of a magnitude permutation in the timing signal is below a reference level corresponding to an engine speed above the idle speed of the engine.
 2. In an internal combustion engine exhibiting periodic engine cycles having a frequency proportional to the speed of the engine and including a throttle member operable to decrease the demand for power from the engine, the combination comprising: fuel injection means for applying fuel to the engine when in an enabled condition and for withholding fuel frOm the engine when in a disabled condition; means for developing a speed signal having an amplitude which increases over the duration of a first fixed portion of each engine cycle such that the amplitude of the speed signal is inversely related to the speed of the engine; means for developing timing pulses each initiated at the expiration of a second fixed portion of each engine cycle which terminates within the first fixed portion; means including a throttle switch operable from a deactuated position to an actuated position in response to a decrease in the demand for power from the engine; and means for placing the fuel injection means in the disabled condition to withhold fuel from the engine when the throttle switch is in the actuated position and the amplitude of the speed signal at the initiation of a timing pulse is below reference level corresponding to an engine speed above the idle speed of the engine.
 3. In an internal combustion engine exhibiting periodic engine cycles having a frequency proportional to the speed of the engine and including a throttle member operable to decrease the demand for power from the engine, the combination comprising: fuel injection means for applying fuel to the engine when in an enabled condition and for withholding fuel from the engine when in a disabled condition; speed signal generator means for developing a speed signal having an amplitude which increases over the duration of a first fixed portion of each engine cycle such that the amplitude of the speed signal is inversely related to the speed of the engine; reference signal generator means for developing a reference signal having an amplitude which is substantially constant at a reference level corresponding to an engine speed above the idle speed of the engine; differential switching means operable to a first state when the amplitude of the reference signal exceeds the amplitude of the speed signal and operable to a second state when the amplitude of the speed signal exceeds the amplitude of the reference signal; timing pulse generator means for developing timing pulses each initiated at the expiration of a second fixed portion of each engine cycle which terminates within the first fixed portion; means including a throttle switch operable from a first position to a second position in response to a decrease in the demand for power from the engine; and means for placing the fuel injection means in the disabled condition to withhold fuel from the engine when the throttle switch is in the second position and the differential switching means is in the first state at the initiation of a timing pulse.
 4. In an internal combustion engine exhibiting periodic engine cycles having a frequency proportional to the speed of the engine and including a throttle member movable to decrease the demand for power from the engine, the combination comprising: fuel injection means for applying fuel to the engine when in an enabled condition and for withholding fuel from the engine when in a disabled condition; speed signal generator means for developing a speed signal having an amplitude which increases from a base level toward a maximum level over the duration of a first fixed portion of each engine cycle such that the amplitude of the speed signal is inversely related to the speed of the engine; reference signal generator means for developing a reference signal having an amplitude which is substantially constant; differential switching means operable to a first state when the amplitude of the reference signal exceeds the amplitude of the speed signal and operable to a second state when the amplitude of the speed signal exceeds the amplitude of the reference signal; timing pulse generator means for developing timing pulses each initiated at the expiration of a second fixed portion of each engine cycle which terminates within the first fixed portion; means including a throttle switch operable from a first position to a second position in response to movement of the throttle member to decrease the Demand for power from he engine; bistable switching means operable to a first state from a second state when the throttle switch is in the second position and the differential switching means is in the first state at the initiation of a timing pulse; means for placing the fuel injection means in the disabled condition to withhold fuel from the engine when the bistable switching means is in the first state; and the reference voltage generator means including means for defining the amplitude of the reference signal at a lower reference level located between the base level and the maximum level at a point corresponding to an engine speed slightly above the idle speed of the engine when the bistable switching means is in the first state and for defining the amplitude of the reference signal at an upper reference level located between the base level and the maximum level at a point corresponding to an engine speed above the peak speed of the engine experienced when fuel is reapplied to the engine after having been withheld from the engine when the bistable switching means is in the second state. 